1. Field of Invention
This invention pertains to large scale displays used, for example, for traffic signs, and more particularly to large scale displays which have elements selectively turned on and off to generate alphanumeric characters or graphic patterns.
2. Description of the Prior Art
Large scale displays are used for various purposes at sports stadiums, on the highways, and so on to display selected messages. Presently, there are two types of displays which are prevalent. One is an electromechanical type formed of a plurality of windows arranged in grids and small two-colored panels arranged behind the windows which can be moved to render each window either color or the other (i.e. black or amber). A disadvantage of this type of display is that since it is mechanical, it requires frequent maintenance. Moreover, at night, external lights are required to illuminate the display. The second prevalent display type consists of a plurality of incandescent bulbs arranged in preselected arrays for example 8.times.5. Various alphanumeric characters can be displayed in each array by selectively energizing some of the bulbs. A problem with this type of display is that the bulbs have a relatively short life and hence must be changed frequently. Another problem is that when incandescent bulbs are used, power consumption is high and excess heat is generated.